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  3. Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recogniz

Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recogniz

admin2014-09-30  27
问题     Left-handers have been the subject of curiosity, stigma and even fear over the centuries. Researchers now, however, are recognizing the scientific importance of understanding why people use one hand or the other to write, eat or toss a ball.
    Handedness, as the dominance of one hand over the other is called, provides a window into the way our brains are wired, experts say. And it may help shed light on disorders related to brain development, like dyslexia(诵读困难症), schizophrenia(精神分裂症)and attention deficit hyperactivity disorder, or ADHD(注意力缺陷多动障碍), which are more common in left-handed people.
    Other recent research suggests that mixed-handedness—using different hands for daily tasks and not having a dominant one—may be even more strongly linked than left-handedness to ADHD and possibly other conditions.
    About 10% of people are left-handed, according to expert estimates. Another 1% of the population is mixed-handed. What causes people not to favor their right hand is only partly due to genetics—even identical twins, who have 100% of the same genes, don’t always share handedness.
    More important, researchers say, are environmental factors—especially stress—in the womb. Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example. And mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child. A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.
    On average there is no significant difference in IQ between righties and lefties, studies show, betraying popular perceptions. There is some evidence that lefties are better at divergent thinking, or starting from existing knowledge to develop new concepts, which is considered an element of creativity. And left-handed people have salaries that on average are about 10% lower than righties, according to recent research performed at Harvard University that analyzed large income data bases, although findings of some earlier studies were mixed.
    Left-handedness appears to be associated with a greater risk for a number of psychiatric and developmental disorders. While lefties make up about 10% of the overall population, about 20% of people with schizophrenia are lefties, for example. Links between left-handedness and dyslexia, ADHD and some mood disorders have also been reported in research studies.
    The reasons for this aren’t clear. Scientists speculate it could be related to a concept known as brain lateralization. The brain has two halves. Each performs primarily separate, specialized functions, such as language processing, which mainly takes place in the left hemisphere. There is lots of communication between the hemispheres.
What can we infer from the last two paragraphs?
选项 A、Brain lateralization makes more people develop dyslexia, ADHD or some mood disorders.
B、It is inevitable for lefties to get psychiatric and developmental disorders related to brain lateralization.
C、Why left-handers are more likely to suffer from psychiatric and developmental disorders may be concerned with brain lateralization.
D、Scientists have proved the association between left-handedness and the risk for psychiatric and developmental disorders.
答案C
解析 细节推断题。倒数第二段说明左撇子与一些精神和发育疾病有关，最后一段接着说明造成这种现象的原因尚不明确，但科学家对此却有推测：左撇子与精神和发育疾病有关联的原因可能与大脑侧化有关。综合上述信息可以推断，C)为正确答案。A)“大脑侧化使更多的人得诵读困难症、注意力缺陷多动障碍和情绪障碍之类的疾病”把大脑侧化、左撇子和这些疾病的因果关系过于绝对化，故排除；B)“左撇子得一些与大脑偏侧性有关的精神和发育疾病是必然的”说法过于绝对，故排除；D)“科学家已经证明左撇子与患精神和发育疾病的风险之间的关系”与本文末段前两句的意思不符，故排除。
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